// Copyright (C) 2016 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
(function() {
  'use strict';

  var CHANGE_ID_ERROR = {
    MISMATCH: 'mismatch',
    MISSING: 'missing',
  };
  var CHANGE_ID_REGEX_PATTERN = /^Change-Id\:\s(I[0-9a-f]{8,40})/gm;
  var COMMENT_SAVE = 'Saving... Try again after all comments are saved.';

  var MIN_LINES_FOR_COMMIT_COLLAPSE = 30;

  // Maximum length for patch set descriptions.
  var PATCH_DESC_MAX_LENGTH = 500;
  var REVIEWERS_REGEX = /^R=/gm;

  Polymer({
    is: 'gr-change-view',

    /**
     * Fired when the title of the page should change.
     *
     * @event title-change
     */

    /**
     * Fired if an error occurs when fetching the change data.
     *
     * @event page-error
     */

    /**
     * Fired if being logged in is required.
     *
     * @event show-auth-required
     */

    properties: {
      /**
       * URL params passed from the router.
       */
      params: {
        type: Object,
        observer: '_paramsChanged',
      },
      viewState: {
        type: Object,
        notify: true,
        value: function() { return {}; },
      },
      backPage: String,
      hasParent: Boolean,
      serverConfig: Object,
      keyEventTarget: {
        type: Object,
        value: function() { return document.body; },
      },

      _account: {
        type: Object,
        value: {},
      },
      _comments: Object,
      _change: {
        type: Object,
        observer: '_changeChanged',
      },
      _commitInfo: Object,
      _files: Object,
      _changeNum: String,
      _diffDrafts: {
        type: Object,
        value: function() { return {}; },
      },
      _editingCommitMessage: {
        type: Boolean,
        value: false,
      },
      _hideEditCommitMessage: {
        type: Boolean,
        computed: '_computeHideEditCommitMessage(_loggedIn, ' +
            '_editingCommitMessage, _change)',
      },
      _latestCommitMessage: {
        type: String,
        value: '',
      },
      _lineHeight: Number,
      _changeIdCommitMessageError: {
        type: String,
        computed:
          '_computeChangeIdCommitMessageError(_latestCommitMessage, _change)',
      },
      _patchRange: {
        type: Object,
        observer: '_updateSelected',
      },
      _relatedChangesLoading: {
        type: Boolean,
        value: true,
      },
      _currentRevisionActions: Object,
      _allPatchSets: {
        type: Array,
        computed: '_computeAllPatchSets(_change, _change.revisions.*)',
      },
      _loggedIn: {
        type: Boolean,
        value: false,
      },
      _loading: Boolean,
      _projectConfig: Object,
      _rebaseOnCurrent: Boolean,
      _replyButtonLabel: {
        type: String,
        value: 'Reply',
        computed: '_computeReplyButtonLabel(_diffDrafts.*)',
      },
      _selectedPatchSet: String,
      _initialLoadComplete: {
        type: Boolean,
        value: false,
      },
      _descriptionReadOnly: {
        type: Boolean,
        computed: '_computeDescriptionReadOnly(_loggedIn, _change, _account)',
      },
      _replyDisabled: {
        type: Boolean,
        value: true,
        computed: '_computeReplyDisabled(serverConfig)',
      },
      _changeStatus: {
        type: String,
        computed: '_computeChangeStatus(_change, _patchRange.patchNum)',
      },
      _commitCollapsed: {
        type: Boolean,
        value: true,
      },
      _relatedChangesCollapsed: {
        type: Boolean,
        value: true,
      },
    },

    behaviors: [
      Gerrit.KeyboardShortcutBehavior,
      Gerrit.PatchSetBehavior,
      Gerrit.RESTClientBehavior,
    ],

    observers: [
      '_labelsChanged(_change.labels.*)',
      '_paramsAndChangeChanged(params, _change)',
    ],

    keyBindings: {
      'shift+r': '_handleCapitalRKey',
      'a': '_handleAKey',
      'd': '_handleDKey',
      's': '_handleSKey',
      'u': '_handleUKey',
      'x': '_handleXKey',
      'z': '_handleZKey',
    },

    attached: function() {
      this._getLoggedIn().then(function(loggedIn) {
        this._loggedIn = loggedIn;
        if (loggedIn) {
          this.$.restAPI.getAccount().then(function(acct) {
            this._account = acct;
          }.bind(this));
        }
      }.bind(this));

      this.addEventListener('comment-save', this._handleCommentSave.bind(this));
      this.addEventListener('comment-discard',
          this._handleCommentDiscard.bind(this));
      this.addEventListener('editable-content-save',
          this._handleCommitMessageSave.bind(this));
      this.addEventListener('editable-content-cancel',
          this._handleCommitMessageCancel.bind(this));
      this.listen(window, 'scroll', '_handleScroll');
    },

    detached: function() {
      this.unlisten(window, 'scroll', '_handleScroll');
    },

    _handleEditCommitMessage: function(e) {
      this._editingCommitMessage = true;
      this.$.commitMessageEditor.focusTextarea();
    },

    _handleCommitMessageSave: function(e) {
      var message = e.detail.content;

      this.$.jsAPI.handleCommitMessage(this._change, message);

      this.$.commitMessageEditor.disabled = true;
      this._saveCommitMessage(message).then(function(resp) {
        this.$.commitMessageEditor.disabled = false;
        if (!resp.ok) { return; }

        this._latestCommitMessage = this._prepareCommitMsgForLinkify(message);
        this._editingCommitMessage = false;
        this._reloadWindow();
      }.bind(this)).catch(function(err) {
        this.$.commitMessageEditor.disabled = false;
      }.bind(this));
    },

    _reloadWindow: function() {
      window.location.reload();
    },

    _handleCommitMessageCancel: function(e) {
      this._editingCommitMessage = false;
    },

    _saveCommitMessage: function(message) {
      return this.$.restAPI.saveChangeCommitMessageEdit(
          this._changeNum, message).then(function(resp) {
            if (!resp.ok) { return resp; }

            return this.$.restAPI.publishChangeEdit(this._changeNum);
          }.bind(this));
    },

    _computeHideEditCommitMessage: function(loggedIn, editing, change) {
      if (!loggedIn || editing || change.status === this.ChangeStatus.MERGED) {
        return true;
      }

      return false;
    },

    _handleCommentSave: function(e) {
      if (!e.target.comment.__draft) { return; }

      var draft = e.target.comment;
      draft.patch_set = draft.patch_set || this._patchRange.patchNum;

      // The use of path-based notification helpers (set, push) can’t be used
      // because the paths could contain dots in them. A new object must be
      // created to satisfy Polymer’s dirty checking.
      // https://github.com/Polymer/polymer/issues/3127
      // TODO(andybons): Polyfill for Object.assign in IE.
      var diffDrafts = Object.assign({}, this._diffDrafts);
      if (!diffDrafts[draft.path]) {
        diffDrafts[draft.path] = [draft];
        this._diffDrafts = diffDrafts;
        return;
      }
      for (var i = 0; i < this._diffDrafts[draft.path].length; i++) {
        if (this._diffDrafts[draft.path][i].id === draft.id) {
          diffDrafts[draft.path][i] = draft;
          this._diffDrafts = diffDrafts;
          return;
        }
      }
      diffDrafts[draft.path].push(draft);
      diffDrafts[draft.path].sort(function(c1, c2) {
        // No line number means that it’s a file comment. Sort it above the
        // others.
        return (c1.line || -1) - (c2.line || -1);
      });
      this._diffDrafts = diffDrafts;
    },

    _handleCommentDiscard: function(e) {
      if (!e.target.comment.__draft) { return; }

      var draft = e.target.comment;
      if (!this._diffDrafts[draft.path]) {
        return;
      }
      var index = -1;
      for (var i = 0; i < this._diffDrafts[draft.path].length; i++) {
        if (this._diffDrafts[draft.path][i].id === draft.id) {
          index = i;
          break;
        }
      }
      if (index === -1) {
        // It may be a draft that hasn’t been added to _diffDrafts since it was
        // never saved.
        return;
      }

      draft.patch_set = draft.patch_set || this._patchRange.patchNum;

      // The use of path-based notification helpers (set, push) can’t be used
      // because the paths could contain dots in them. A new object must be
      // created to satisfy Polymer’s dirty checking.
      // https://github.com/Polymer/polymer/issues/3127
      // TODO(andybons): Polyfill for Object.assign in IE.
      var diffDrafts = Object.assign({}, this._diffDrafts);
      diffDrafts[draft.path].splice(index, 1);
      if (diffDrafts[draft.path].length === 0) {
        delete diffDrafts[draft.path];
      }
      this._diffDrafts = diffDrafts;
    },

    _handlePatchChange: function(e) {
      this._changePatchNum(parseInt(e.target.value, 10), true);
    },

    _handleReplyTap: function(e) {
      e.preventDefault();
      this._openReplyDialog();
    },

    _handleDownloadTap: function(e) {
      e.preventDefault();
      this.$.downloadOverlay.open().then(function() {
        this.$.downloadOverlay
            .setFocusStops(this.$.downloadDialog.getFocusStops());
        this.$.downloadDialog.focus();
      }.bind(this));
    },

    _handleDownloadDialogClose: function(e) {
      this.$.downloadOverlay.close();
    },

    _handleMessageReply: function(e) {
      var msg = e.detail.message.message;
      var quoteStr = msg.split('\n').map(
          function(line) { return '> ' + line; }).join('\n') + '\n\n';

      if (quoteStr !== this.$.replyDialog.quote) {
        this.$.replyDialog.draft = quoteStr;
      }
      this.$.replyDialog.quote = quoteStr;
      this._openReplyDialog();
    },

    _handleReplyOverlayOpen: function(e) {
      this.$.replyDialog.focus();
    },

    _handleReplySent: function(e) {
      this.$.replyOverlay.close();
      this._reload();
    },

    _handleReplyCancel: function(e) {
      this.$.replyOverlay.close();
    },

    _handleReplyAutogrow: function(e) {
      this.$.replyOverlay.refit();
    },

    _handleShowReplyDialog: function(e) {
      var target = this.$.replyDialog.FocusTarget.REVIEWERS;
      if (e.detail.value && e.detail.value.ccsOnly) {
        target = this.$.replyDialog.FocusTarget.CCS;
      }
      this._openReplyDialog(target);
    },

    _handleScroll: function() {
      this.debounce('scroll', function() {
        history.replaceState(
            {
              scrollTop: document.body.scrollTop,
              path: location.pathname,
            },
            location.pathname);
      }, 150);
    },

    _paramsChanged: function(value) {
      if (value.view !== this.tagName.toLowerCase()) {
        this._initialLoadComplete = false;
        return;
      }

      var patchChanged = this._patchRange &&
          (value.patchNum !== undefined && value.basePatchNum !== undefined) &&
          (this._patchRange.patchNum !== value.patchNum ||
          this._patchRange.basePatchNum !== value.basePatchNum);

      if (this._changeNum !== value.changeNum) {
        this._initialLoadComplete = false;
      }

      var patchRange = {
        patchNum: value.patchNum,
        basePatchNum: value.basePatchNum || 'PARENT',
      };

      if (this._initialLoadComplete && patchChanged) {
        if (patchRange.patchNum == null) {
          patchRange.patchNum = this._computeLatestPatchNum(this._allPatchSets);
        }
        this._patchRange = patchRange;
        this._reloadPatchNumDependentResources().then(function() {
          this.$.jsAPI.handleEvent(this.$.jsAPI.EventType.SHOW_CHANGE, {
            change: this._change,
            patchNum: patchRange.patchNum,
          });
        }.bind(this));
        return;
      }

      this._changeNum = value.changeNum;
      this._patchRange = patchRange;
      this.$.relatedChanges.clear();

      this._reload().then(function() {
        this._performPostLoadTasks();
      }.bind(this));
    },

    _performPostLoadTasks: function() {
      // Allow the message list and related changes to render before scrolling.
      // Related changes are loaded here (after everything else) because they
      // take the longest and are secondary information. Because the element may
      // alter the total height of the page, the call to potentially scroll to
      // a linked message is performed after related changes is fully loaded.
      this.$.relatedChanges.reload().then(function() {
        this.async(function() {
          if (history.state && history.state.scrollTop) {
            document.documentElement.scrollTop =
                document.body.scrollTop = history.state.scrollTop;
          } else {
            this._maybeScrollToMessage();
          }
        }, 1);
      }.bind(this));

      this._maybeShowReplyDialog();

      this._maybeShowRevertDialog();

      this.$.jsAPI.handleEvent(this.$.jsAPI.EventType.SHOW_CHANGE, {
        change: this._change,
        patchNum: this._patchRange.patchNum,
      });

      this._initialLoadComplete = true;
    },

    _paramsAndChangeChanged: function(value) {
      // If the change number or patch range is different, then reset the
      // selected file index.
      var patchRangeState = this.viewState.patchRange;
      if (this.viewState.changeNum !== this._changeNum ||
          patchRangeState.basePatchNum !== this._patchRange.basePatchNum ||
          patchRangeState.patchNum !== this._patchRange.patchNum) {
        this._resetFileListViewState();
      }
    },

    _maybeScrollToMessage: function() {
      var msgPrefix = '#message-';
      var hash = window.location.hash;
      if (hash.indexOf(msgPrefix) === 0) {
        this.$.messageList.scrollToMessage(hash.substr(msgPrefix.length));
      }
    },

    _getLocationSearch: function() {
      // Not inlining to make it easier to test.
      return window.location.search;
    },

    _getUrlParameter: function(param) {
      var pageURL = this._getLocationSearch().substring(1);
      var vars = pageURL.split('&');
      for (var i = 0; i < vars.length; i++) {
        var name = vars[i].split('=');
        if (name[0] == param) {
          return name[0];
        }
      }
      return null;
    },

    _maybeShowRevertDialog: function() {
      Gerrit.awaitPluginsLoaded()
        .then(this._getLoggedIn.bind(this))
        .then(function(loggedIn) {
          if (!loggedIn || this._change.status !== this.ChangeStatus.MERGED) {
            // Do not display dialog if not logged-in or the change is not
            // merged.
            return;
          }
          if (!!this._getUrlParameter('revert')) {
            this.$.actions.showRevertDialog();
          }
        }.bind(this));
    },

    _maybeShowReplyDialog: function() {
      this._getLoggedIn().then(function(loggedIn) {
        if (!loggedIn) { return; }

        if (this.viewState.showReplyDialog) {
          this._openReplyDialog();
          this.async(function() { this.$.replyOverlay.center(); }, 1);
          this.set('viewState.showReplyDialog', false);
        }
      }.bind(this));
    },

    _resetFileListViewState: function() {
      this.set('viewState.selectedFileIndex', 0);
      if (!!this.viewState.changeNum &&
          this.viewState.changeNum !== this._changeNum) {
        // Reset the diff mode to null when navigating from one change to
        // another, so that the user's preference is restored.
        this.set('viewState.diffMode', null);
      }
      this.set('viewState.changeNum', this._changeNum);
      this.set('viewState.patchRange', this._patchRange);
    },

    _changeChanged: function(change) {
      if (!change) { return; }
      this.set('_patchRange.basePatchNum',
          this._patchRange.basePatchNum || 'PARENT');
      this.set('_patchRange.patchNum',
          this._patchRange.patchNum ||
              this._computeLatestPatchNum(this._allPatchSets));

      this._updateSelected();

      var title = change.subject + ' (' + change.change_id.substr(0, 9) + ')';
      this.fire('title-change', {title: title});
    },

    /**
     * Change active patch to the provided patch num.
     * @param {number} patchNum the patchn number to be viewed.
     * @param {boolean} opt_forceParams When set to true, the resulting URL will
     *     always include the patch range, even if the requested patchNum is
     *     known to be the latest.
     */
    _changePatchNum: function(patchNum, opt_forceParams) {
      if (!opt_forceParams) {
        var currentPatchNum;
        if (this._change.current_revision) {
          currentPatchNum =
              this._change.revisions[this._change.current_revision]._number;
        } else {
          currentPatchNum = this._computeLatestPatchNum(this._allPatchSets);
        }
        if (patchNum === currentPatchNum &&
            this._patchRange.basePatchNum === 'PARENT') {
          page.show(this.changePath(this._changeNum));
          return;
        }
      }
      var patchExpr = this._patchRange.basePatchNum === 'PARENT' ? patchNum :
          this._patchRange.basePatchNum + '..' + patchNum;
      page.show(this.changePath(this._changeNum) + '/' + patchExpr);
    },

    _computeChangePermalink: function(changeNum) {
      return '/' + changeNum;
    },

    _computeChangeStatus: function(change, patchNum) {
      var statusString;
      if (change.status === this.ChangeStatus.NEW) {
        var rev = this.getRevisionByPatchNum(change.revisions, patchNum);
        if (rev && rev.draft === true) {
          statusString = 'Draft';
        }
      } else {
        statusString = this.changeStatusString(change);
      }
      return statusString || '';
    },

    _computeShowCommitInfo: function(changeStatus, current_revision) {
      return changeStatus === 'Merged' && current_revision;
    },

    _computeMergedCommitInfo: function(current_revision, revisions) {
      var rev = revisions[current_revision];
      if (!rev || !rev.commit) { return {}; }
      // CommitInfo.commit is optional. Set commit in all cases to avoid error
      // in <gr-commit-info>. @see Issue 5337
      if (!rev.commit.commit) { rev.commit.commit = current_revision; }
      return rev.commit;
    },

    _computeChangeIdClass: function(displayChangeId) {
      return displayChangeId === CHANGE_ID_ERROR.MISMATCH ? 'warning' : '';
    },

    _computeTitleAttributeWarning: function(displayChangeId) {
      if (displayChangeId === CHANGE_ID_ERROR.MISMATCH) {
        return 'Change-Id mismatch';
      } else if (displayChangeId === CHANGE_ID_ERROR.MISSING) {
        return 'No Change-Id in commit message';
      }
    },

    _computeChangeIdCommitMessageError: function(commitMessage, change) {
      if (!commitMessage) { return CHANGE_ID_ERROR.MISSING; }

      // Find the last match in the commit message:
      var changeId;
      var changeIdArr;

      while (changeIdArr = CHANGE_ID_REGEX_PATTERN.exec(commitMessage)) {
        changeId = changeIdArr[1];
      }

      if (changeId) {
        // A change-id is detected in the commit message.

        if (changeId === change.change_id) {
          // The change-id found matches the real change-id.
          return null;
        }
        // The change-id found does not match the change-id.
        return CHANGE_ID_ERROR.MISMATCH;
      }
      // There is no change-id in the commit message.
      return CHANGE_ID_ERROR.MISSING;
    },

    _computeLatestPatchNum: function(allPatchSets) {
      return allPatchSets[allPatchSets.length - 1].num;
    },

    _computePatchInfoClass: function(patchNum, allPatchSets) {
      if (parseInt(patchNum, 10) ===
          this._computeLatestPatchNum(allPatchSets)) {
        return '';
      }
      return 'patchInfo--oldPatchSet';
    },

    /**
     * Determines if a patch number should be disabled based on value of the
     * basePatchNum from gr-file-list.
     * @param {Number} patchNum Patch number available in dropdown
     * @param {Number|String} basePatchNum Base patch number from file list
     * @return {Boolean}
     */
    _computePatchSetDisabled: function(patchNum, basePatchNum) {
      basePatchNum = basePatchNum === 'PARENT' ? 0 : basePatchNum;
      return parseInt(patchNum, 10) <= parseInt(basePatchNum, 10);
    },

    _computeAllPatchSets: function(change) {
      var patchNums = [];
      for (var commit in change.revisions) {
        if (change.revisions.hasOwnProperty(commit)) {
          patchNums.push({
            num: change.revisions[commit]._number,
            desc: change.revisions[commit].description,
          });
        }
      }
      return patchNums.sort(function(a, b) { return a.num - b.num; });
    },

    _computeLabelNames: function(labels) {
      return Object.keys(labels).sort();
    },

    _computeLabelValues: function(labelName, labels) {
      var result = [];
      var t = labels[labelName];
      if (!t) { return result; }
      var approvals = t.all || [];
      approvals.forEach(function(label) {
        if (label.value && label.value != labels[labelName].default_value) {
          var labelClassName;
          var labelValPrefix = '';
          if (label.value > 0) {
            labelValPrefix = '+';
            labelClassName = 'approved';
          } else if (label.value < 0) {
            labelClassName = 'notApproved';
          }
          result.push({
            value: labelValPrefix + label.value,
            className: labelClassName,
            account: label,
          });
        }
      });
      return result;
    },

    _computeReplyButtonLabel: function(changeRecord) {
      var drafts = (changeRecord && changeRecord.base) || {};
      var draftCount = Object.keys(drafts).reduce(function(count, file) {
        return count + drafts[file].length;
      }, 0);

      var label = 'Reply';
      if (draftCount > 0) {
        label += ' (' + draftCount + ')';
      }
      return label;
    },

    _handleAKey: function(e) {
      if (this.shouldSuppressKeyboardShortcut(e) ||
          this.modifierPressed(e)) {
        return;
      }
      this._getLoggedIn().then(function(isLoggedIn) {
        if (!isLoggedIn) {
          this.fire('show-auth-required');
          return;
        }

        e.preventDefault();
        this._openReplyDialog();
      }.bind(this));
    },

    _handleDKey: function(e) {
      if (this.shouldSuppressKeyboardShortcut(e) ||
          this.modifierPressed(e)) { return; }

      e.preventDefault();
      this.$.downloadOverlay.open();
    },

    _handleCapitalRKey: function(e) {
      if (this.shouldSuppressKeyboardShortcut(e)) { return; }
      e.preventDefault();
      page.show('/c/' + this._change._number);
    },

    _handleSKey: function(e) {
      if (this.shouldSuppressKeyboardShortcut(e) ||
          this.modifierPressed(e)) { return; }

      e.preventDefault();
      this.$.changeStar.toggleStar();
    },

    _handleUKey: function(e) {
      if (this.shouldSuppressKeyboardShortcut(e)) { return; }

      e.preventDefault();
      this._determinePageBack();
    },

    _handleXKey: function(e) {
      if (this.shouldSuppressKeyboardShortcut(e) ||
          this.modifierPressed(e)) { return; }

      e.preventDefault();
      this.$.messageList.handleExpandCollapse(true);
    },

    _handleZKey: function(e) {
      if (this.shouldSuppressKeyboardShortcut(e) ||
          this.modifierPressed(e)) { return; }

      e.preventDefault();
      this.$.messageList.handleExpandCollapse(false);
    },

    _determinePageBack: function() {
      // Default backPage to '/' if user came to change view page
      // via an email link, etc.
      page.show(this.backPage || '/');
    },

    _handleLabelRemoved: function(splices, path) {
      for (var i = 0; i < splices.length; i++) {
        var splice = splices[i];
        for (var j = 0; j < splice.removed.length; j++) {
          var removed = splice.removed[j];
          var changePath = path.split('.');
          var labelPath = changePath.splice(0, changePath.length - 2);
          var labelDict = this.get(labelPath);
          if (labelDict.approved &&
              labelDict.approved._account_id === removed._account_id) {
            this._reload();
            return;
          }
        }
      }
    },

    _labelsChanged: function(changeRecord) {
      if (!changeRecord) { return; }
      if (changeRecord.value.indexSplices) {
        this._handleLabelRemoved(changeRecord.value.indexSplices,
            changeRecord.path);
      }
      this.$.jsAPI.handleEvent(this.$.jsAPI.EventType.LABEL_CHANGE, {
        change: this._change,
      });
    },

    _openReplyDialog: function(opt_section) {
      if (this.$.restAPI.hasPendingDiffDrafts()) {
        this.dispatchEvent(new CustomEvent('show-alert',
            {detail: {message: COMMENT_SAVE}, bubbles: true}));
        return;
      }
      this.$.replyOverlay.open().then(function() {
        this.$.replyOverlay.setFocusStops(this.$.replyDialog.getFocusStops());
        this.$.replyDialog.open(opt_section);
      }.bind(this));
    },

    _handleReloadChange: function(e) {
      return this._reload().then(function() {
        // If the change was rebased, we need to reload the page with the
        // latest patch.
        if (e.detail.action === 'rebase') {
          page.show(this.changePath(this._changeNum));
        }
      }.bind(this));
    },

    _handleGetChangeDetailError: function(response) {
      this.fire('page-error', {response: response});
    },

    _getDiffDrafts: function() {
      return this.$.restAPI.getDiffDrafts(this._changeNum).then(
          function(drafts) {
            return this._diffDrafts = drafts;
          }.bind(this));
    },

    _getLoggedIn: function() {
      return this.$.restAPI.getLoggedIn();
    },

    _getProjectConfig: function() {
      return this.$.restAPI.getProjectConfig(this._change.project).then(
          function(config) {
            this._projectConfig = config;
          }.bind(this));
    },

    _updateRebaseAction: function(revisionActions) {
      if (revisionActions && revisionActions.rebase) {
        revisionActions.rebase.rebaseOnCurrent =
            !!revisionActions.rebase.enabled;
        revisionActions.rebase.enabled = true;
      }
      return revisionActions;
    },

    _prepareCommitMsgForLinkify: function(msg) {
      // TODO(wyatta) switch linkify sequence, see issue 5526.
      // This is a zero-with space. It is added to prevent the linkify library
      // from including R= as part of the email address.
      return msg.replace(REVIEWERS_REGEX, 'R=\u200B');
    },

    _getChangeDetail: function() {
      return this.$.restAPI.getChangeDetail(this._changeNum,
          this._handleGetChangeDetailError.bind(this)).then(
              function(change) {
                // Issue 4190: Coalesce missing topics to null.
                if (!change.topic) { change.topic = null; }
                if (!change.reviewer_updates) {
                  change.reviewer_updates = null;
                }
                var latestRevisionSha = this._getLatestRevisionSHA(change);
                var currentRevision = change.revisions[latestRevisionSha];
                if (currentRevision.commit && currentRevision.commit.message) {
                  this._latestCommitMessage = this._prepareCommitMsgForLinkify(
                      currentRevision.commit.message);
                } else {
                  this._latestCommitMessage = null;
                }
                var lineHeight = getComputedStyle(this).lineHeight;
                this._lineHeight = lineHeight.slice(0, lineHeight.length - 2);

                this._change = change;
                if (!this._patchRange || !this._patchRange.patchNum ||
                    this._patchRange.patchNum === currentRevision._number) {
                  // CommitInfo.commit is optional, and may need patching.
                  if (!currentRevision.commit.commit) {
                    currentRevision.commit.commit = latestRevisionSha;
                  }
                  this._commitInfo = currentRevision.commit;
                  this._currentRevisionActions =
                      this._updateRebaseAction(currentRevision.actions);
                  // TODO: Fetch and process files.
                }
              }.bind(this));
    },

    _getComments: function() {
      return this.$.restAPI.getDiffComments(this._changeNum).then(
          function(comments) {
            this._comments = comments;
          }.bind(this));
    },

    _getLatestCommitMessage: function() {
      return this.$.restAPI.getChangeCommitInfo(this._changeNum,
          this._computeLatestPatchNum(this._allPatchSets)).then(
              function(commitInfo) {
                this._latestCommitMessage =
                    this._prepareCommitMsgForLinkify(commitInfo.message);
              }.bind(this));
    },

    _getLatestRevisionSHA: function(change) {
      if (change.current_revision) {
        return change.current_revision;
      }
      // current_revision may not be present in the case where the latest rev is
      // a draft and the user doesn’t have permission to view that rev.
      var latestRev = null;
      var latestPatchNum = -1;
      for (var rev in change.revisions) {
        if (!change.revisions.hasOwnProperty(rev)) { continue; }

        if (change.revisions[rev]._number > latestPatchNum) {
          latestRev = rev;
          latestPatchNum = change.revisions[rev]._number;
        }
      }
      return latestRev;
    },

    _getCommitInfo: function() {
      return this.$.restAPI.getChangeCommitInfo(
          this._changeNum, this._patchRange.patchNum).then(
              function(commitInfo) {
                this._commitInfo = commitInfo;
              }.bind(this));
    },

    _reloadDiffDrafts: function() {
      this._diffDrafts = {};
      this._getDiffDrafts().then(function() {
        if (this.$.replyOverlay.opened) {
          this.async(function() { this.$.replyOverlay.center(); }, 1);
        }
      }.bind(this));
    },

    _reload: function() {
      this._loading = true;
      this._relatedChangesCollapsed = true;

      this._getLoggedIn().then(function(loggedIn) {
        if (!loggedIn) { return; }

        this._reloadDiffDrafts();
      }.bind(this));

      var detailCompletes = this._getChangeDetail().then(function() {
        this._loading = false;
        this._getProjectConfig();
      }.bind(this));
      this._getComments();

      if (this._patchRange.patchNum) {
        return Promise.all([
          this._reloadPatchNumDependentResources(),
          detailCompletes,
        ]).then(function() {
          return this.$.actions.reload();
        }.bind(this));
      } else {
        // The patch number is reliant on the change detail request.
        return detailCompletes.then(function() {
          this.$.fileList.reload();
          if (!this._latestCommitMessage) {
            this._getLatestCommitMessage();
          }
        }.bind(this));
      }
    },

    /**
     * Kicks off requests for resources that rely on the patch range
     * (`this._patchRange`) being defined.
     */
    _reloadPatchNumDependentResources: function() {
      return Promise.all([
        this._getCommitInfo(),
        this.$.fileList.reload(),
      ]);
    },

    _updateSelected: function() {
      this._selectedPatchSet = this._patchRange.patchNum;
    },

    _computePatchSetDescription: function(change, patchNum) {
      var rev = this.getRevisionByPatchNum(change.revisions, patchNum);
      return (rev && rev.description) ?
          rev.description.substring(0, PATCH_DESC_MAX_LENGTH) : '';
    },

    _computeDescriptionPlaceholder: function(readOnly) {
      return (readOnly ? 'No' : 'Add a') + ' patch set description';
    },

    _handleDescriptionChanged: function(e) {
      var desc = e.detail.trim();
      var rev = this.getRevisionByPatchNum(this._change.revisions,
          this._selectedPatchSet);
      var sha = this._getPatchsetHash(this._change.revisions, rev);
      this.$.restAPI.setDescription(this._changeNum,
          this._selectedPatchSet, desc)
          .then(function(res) {
            if (res.ok) {
              this.set(['_change', 'revisions', sha, 'description'], desc);
            }
          }.bind(this));
    },


    /**
     * @param {Object} revisions The revisions object keyed by revision hashes
     * @param {Object} patchSet A revision already fetched from {revisions}
     * @return {string} the SHA hash corresponding to the revision.
     */
    _getPatchsetHash: function(revisions, patchSet) {
      for (var rev in revisions) {
        if (revisions.hasOwnProperty(rev) &&
            revisions[rev] === patchSet) {
          return rev;
        }
      }
    },

    _computeDescriptionReadOnly: function(loggedIn, change, account) {
      return !(loggedIn && (account._account_id === change.owner._account_id));
    },

    _computeReplyDisabled: function() { return false; },

    _computeChangePermalinkAriaLabel: function(changeNum) {
      return 'Change ' + changeNum;
    },

    _computeCommitClass: function(collapsed, commitMessage) {
      if (this._computeCommitToggleHidden(commitMessage)) { return ''; }
      return collapsed ? 'collapsed' : '';
    },

    _computeRelatedChangesClass: function(collapsed, loading) {
      if (!loading && !this.customStyle['--relation-chain-max-height']) {
        this._updateRelatedChangeMaxHeight();
      }
      return collapsed ? 'collapsed' : '';
    },

    _computeCollapseText: function(collapsed) {
      // Symbols are up and down triangles.
      return collapsed ? '\u25bc Show more' : '\u25b2 Show less';
    },

    _toggleCommitCollapsed: function() {
      this._commitCollapsed = !this._commitCollapsed;
      if (this._commitCollapsed) {
        window.scrollTo(0, 0);
      }
    },

    _toggleRelatedChangesCollapsed: function() {
      this._relatedChangesCollapsed = !this._relatedChangesCollapsed;
      if (this._relatedChangesCollapsed) {
        window.scrollTo(0, 0);
      }
    },

    _computeCommitToggleHidden: function(commitMessage) {
      if (!commitMessage) { return true; }
      return commitMessage.split('\n').length < MIN_LINES_FOR_COMMIT_COLLAPSE;
    },

    _getOffsetHeight: function(element) {
      return element.offsetHeight;
    },

    _getScrollHeight: function(element) {
      return element.scrollHeight;
    },

    /**
     * @desc get the line height of an element to the nearest integer.
     * */
    _getLineHeight: function(element) {
      var lineHeightStr = getComputedStyle(element).lineHeight;
      return Math.round(lineHeightStr.slice(0, lineHeightStr.length - 2));
    },

    /**
     * @desc new max height for the related changes section, shorter than
     * the existing change info height.
     */
    _updateRelatedChangeMaxHeight: function() {
      // Takes into account approximate height for the expand button and
      // bottom margin
      var extraHeight = 24;
      var maxExistingHeight;
      var hasCommitToggle =
          !this._computeCommitToggleHidden(this._latestCommitMessage);
      if (hasCommitToggle) {
        // Make sure the content is lined up if both areas have buttons. If the
        // commit message is not collapsed, instead use the change info hight.
        maxExistingHeight = this._getOffsetHeight(this.$.commitMessage);
      } else {
        maxExistingHeight = this._getOffsetHeight(this.$.mainChangeInfo) -
            extraHeight;
      }

      // Get the line height of related changes, and convert it to the nearest
      // integer.
      var lineHeight = this._getLineHeight(this.$.relatedChanges);

      // Figure out a new height that is divisible by the rounded line height.
      var remainder = maxExistingHeight % lineHeight;
      var newHeight = maxExistingHeight - remainder;

      // Update the max-height of the relation chain to this new height;
      this.customStyle['--relation-chain-max-height'] = newHeight + 'px';
      if (hasCommitToggle) {
        this.customStyle['--related-change-btn-top-padding'] = remainder + 'px';
      }
      this.updateStyles();
    },

    _computeRelatedChangesToggleHidden: function() {
      return this._getScrollHeight(this.$.relatedChanges) <=
          this._getOffsetHeight(this.$.relatedChanges);
    },
  });
})();